Heteroepitaxy, a process for crystalline film growth on a crystalline substrate of a film of a different material than the substrate, has many practical applications. For example, germanium (Ge) heteroepitaxy on silicon (Si) is used as p-channel in field effect transistors (FET). However, heteroepitaxially grown films are prone to defects, such as dislocations, anti-phase boundaries, and stacking faults, due to the lattice mismatch between the crystalline materials.
Aspect ratio trapping (ART) has been used to reduce defects in heteroepitaxially grown films (heteroepitaxial film). In aspect ratio trapping, a crystalline material grows in deep, narrow, i.e. high aspect ratio, trenches so that some dislocations caused by lattice mismatch may terminate at the trench walls, thus, trapped in the high aspect ratio trenches rather than running up into active channel area of the device/crystalline material.
However, conventional aspect ratio trapping cannot terminate dislocations generated in along the length of the narrow trenches. Therefore, there is a need for methods and structures with reduced defects in a heteroepitaxial film.